Reciprocating refrigeration compressor motor winding insulation test and overheating protection setting

Reciprocating refrigeration compressor motor winding insulation test and overheating protection setting

Motor is the power source of reciprocating refrigeration compressor; winding insulation degradation is mainly caused by moisture ingress, overheating and chemical corrosion from refrigerant and lubricant. The minimum acceptable insulation resistance for compressor motor winding at 25℃ is 1 MΩ; insulation resistance below 0.5 MΩ means winding has hidden leakage risk and cannot start. Xiteliduo reciprocating compressor motor is equipped with embedded PTC temperature sensors inside windings; winding temperature above 155℃ will trigger motor overheat protection shutdown. Small 4-cyl reciprocating refrigeration compressor motor insulation failure frequently occurs after long shutdown; moisture accumulates inside stator and reduces insulation resistance sharply. Medium 4-cyl reciprocating refrigeration compressor motor overloading under high compression ratio will continuously heat windings; sustained temperature above 140℃ accelerates insulation aging by 6 times. Large 4-cyl reciprocating refrigeration compressor uses separate motor forced air cooling; fan failure will rapidly raise winding temperature and shorten insulation service life. Large 6-cyl reciprocating refrigeration compressor with high rated current needs regular three-phase current balance check; current unbalance exceeding 8% will produce local hot spots on windings. Many maintenance teams only test insulation resistance after motor fault. Periodic insulation test can reduce motor sudden failure probability by 57%. Single-unit two-stage refrigeration compressor low-stage motor runs at lower ambient temperature; refrigerant leakage into motor cavity will dissolve insulation varnish. Cascade unit high-stage reciprocating refrigeration compressor motor bears higher operating load; thermal protection parameters need to be matched with high compression ratio working condition.

FAQ

Q1: What is the minimum acceptable motor winding insulation resistance at 25℃? A1: The insulation resistance shall not be lower than 1 MΩ. Q2: What protection threshold is set for Xiteliduo reciprocating compressor embedded winding PTC sensor? A2: Protection shutdown activates when winding temperature exceeds 155℃. Q3: Why does small 4-cyl reciprocating compressor motor insulation drop after long standby? A3: Moisture accumulates inside the stator and degrades insulation performance. Q4: How much faster will insulation degrade if medium 4-cyl compressor winding stays above 140℃ continuously? A4: Insulation aging speed increases by 6 times. Q5: What three-phase current unbalance threshold will create winding local hot spots? A5: Three-phase current unbalance over 8% will generate local hot spots. Q6: What benefit can periodic motor insulation resistance test bring? A6: It can reduce sudden motor failure probability by 57%. Q7: What damage will refrigerant leakage bring to low-stage motor of single-unit two-stage compressor? A7: Refrigerant entering motor cavity dissolves winding insulation varnish.